The invention relates to a process for recycling fine-particle solids, such as coal dust, discharged from a reactor vessel, particularly from a melter gasifier, at a discharging position of the reactor vessel by means of a gas, at a recycling position of the reactor vessel, wherein the solids are separated in a solids separator, particularly a cyclone, subsequently collected in a collecting vessel and from the same are recycled into the reactor vessel by means of a conveying gas while maintaining a difference in pressure between the solids separator and the recycling position and an arrangement for carrying out the process.
From EP-A - 0 493 752 it is known to separate hot dusts from a gasification reactor, such as a melter gasifier, in a cyclone and in order to surmount a difference of pressure between the cyclone and the gasifier recirculate them via a sluice system, namely via a burner. The known sluice system is very expensive in construction, the mechanically operated sluices being moreover exposed to substantial wear by the dustlike solids.
From EP-B - 0 278 287 a process of the initially described kind is known. Here, the solids incurring in the solids separator after separation from the offgas carried out of the reactor vessel are collected in a collecting vessel, wherein between the separator, which is constructed as a cyclone, and the collecting vessel the pressure is lowered to a level equal to the lowest pressure in the solids separator or optionally lower than this pressure by effecting gas exhaustion at a distance from the separator. Although this process offers the advantage that the solids leaving the solids separator can flow into the collecting vessel freely, since between the solids separator and the collecting vessel there is no upward gas flow that would hamper the movement of the solid particles, it still involves the disadvantage that due to the lower pressure offgas from the reactor vessel passes through the cyclone and together with the recycled solids is recycled into the same again, such that processes taking place in the reactor vessel are disturbed or at least are less efficient due to the recycling of already spent gases.
From EP-B - 0 245 268 it is known to conduct the flue gases emerging from a reactor vessel to a cyclone separator, which then recycles separated solid particles into the reactor vessel again. A portion of the solid particles is discharged from the cyclone separator by suction separately from the rest of the solid particles along with flue gas and recycled into the reactor vessel separately. Here, too, in addition to recycling of the solid particles recycling of a considerable portion of the flue gas into the reactor occurs, which in turn increases the gas throughput through the reactor of gas portions that are inert with regard to the reactions taking place in the reactor and entails a lower efficiency of the processes taking place in the reactor.
The invention aims at avoiding these disadvantages and difficulties and has as its object to enhance the functioning of the solids separator and recirculate the solids into the reactor in a stable conveying condition, wherein there is to be avoided on the one hand an additional load on the reactor vessel due to reactor offgas already spent in the reactor in the course of different reaction processes or, on the other hand, if a specific product gas is to be produced in the reactor, a yield loss in terms of product gas.